U.S. patent application number 15/353850 was filed with the patent office on 2018-05-17 for interconnect structure including air gap.
The applicant listed for this patent is TAIWAN SEMICONDUCTOR MANUFACTURING CO., LTD.. Invention is credited to Hsin-Ping Chen, Wei-Chen Chu, Chung-Ju Lee, Chih-Wei Lu, Tai-I Yang.
Application Number | 20180138076 15/353850 |
Document ID | / |
Family ID | 62107665 |
Filed Date | 2018-05-17 |
United States Patent
Application |
20180138076 |
Kind Code |
A1 |
Yang; Tai-I ; et
al. |
May 17, 2018 |
INTERCONNECT STRUCTURE INCLUDING AIR GAP
Abstract
A method of forming a semiconductor structure is provided. A
conductive layer is formed over a substrate. The conductive layer
is selectively etched to form a first conductive portion, a second
conductive portion, and a spacing between the first conductive
portion and the second conductive portion. A dielectric layer is
formed over the first conductive portion, the second conductive
portion, and the spacing, such that an air gap is formed in the
spacing between the first and second conductive portions and is
sealed by the dielectric layer.
Inventors: |
Yang; Tai-I; (Hsinchu City,
TW) ; Chu; Wei-Chen; (Taichung City, TW) ;
Chen; Hsin-Ping; (Hsinchu County, TW) ; Lu;
Chih-Wei; (Hsinchu City, TW) ; Lee; Chung-Ju;
(Hsinchu City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TAIWAN SEMICONDUCTOR MANUFACTURING CO., LTD. |
Hsinchu |
|
TW |
|
|
Family ID: |
62107665 |
Appl. No.: |
15/353850 |
Filed: |
November 17, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/76852 20130101;
H01L 21/7682 20130101; H01L 21/76885 20130101; H01L 23/5283
20130101 |
International
Class: |
H01L 21/768 20060101
H01L021/768; H01L 23/522 20060101 H01L023/522; H01L 23/528 20060101
H01L023/528; H01L 23/532 20060101 H01L023/532 |
Claims
1. A method of forming an interconnect structure, comprising:
forming a conductive layer over a substrate; selectively etching
the conductive layer to form a first conductive portion, a second
conductive portion, and a spacing between the first conductive
portion and the second conductive portion; removing a first portion
of the substrate under the spacing, while remaining a second
portion of the substrate under the first conductive portion, such
that a sidewall of the second portion of the substrate has a
different shape from a sidewall of the first conductive portion;
and forming a dielectric layer over the first conductive portion,
the second conductive portion, and the spacing, such that an air
gap is formed in the spacing between the first and second
conductive portions and is sealed by the dielectric layer.
2. The method according to claim 1, further comprising forming a
metal capping layer covering the first and second conductive
portions after selectively etching the conductive layer.
3. (canceled)
4. The method according to claim 1, wherein the spacing comprises
an inlet and a bottom, and a width of the inlet is greater than a
width of the bottom.
5-20. (canceled)
21. A method of forming a semiconductor structure, comprising:
forming a first dielectric layer over a substrate; forming a via
opening in the first dielectric layer; overfilling the via opening
with a conductive layer; etching the conductive layer to form
separated first and second conductive portions; and forming a
second dielectric layer over the separated first and second
conductive portions such that an air gap is formed under the second
dielectric layer and between the separated first and second
conductive portions, and such that the air gap extends to higher
elevation than a top of the first conductive portion.
22. The method of claim 21, wherein the forming the second
dielectric layer comprises spin-on coating a dielectric material on
the first dielectric layer and the separated first and second
conductive portions.
23. The method of claim 22, wherein the spin-on coating is
performed such that the dielectric material is formed on a sidewall
of the first conductive portion farthest away from the second
conductive portion.
24. The method of claim 21, wherein the etching the conductive
layer stops until reaching the first dielectric layer.
25. The method of claim 21, wherein the forming the first
dielectric layer comprises forming a low-k dielectric layer over
the substrate and forming an etch stop layer over the low-k
dielectric layer, wherein the etching the conductive layer stops
until reaching the etch stop layer.
26. The method of claim 25, wherein a portion of the etch stop
layer is exposed after the etching the conductive layer, and the
method further comprises removing the exposed portion of the etch
stop layer such that a portion of the low-k dielectric layer is
exposed.
27. The method of claim 26, wherein the forming of the second
dielectric layer comprises spin-coating a dielectric material on
the exposed portion of the low-k dielectric layer.
28. The method of claim 21, wherein an etchant used in the etching
the conductive layer comprises at least one of Cl2, F2, H2, and
CxFy.
29. The method of claim 21, wherein the etching the conductive
layer is a reactive ion etching (ME) process using at least one of
Cl2, F2, H2, and CxFy as an etchant.
30. The method of claim 21, further comprising performing a
chemical mechanical polishing (CMP) process to the conductive layer
prior to the etching the conductive layer.
31. The method of claim 30, wherein the CMP process stops at a
position higher than a top surface of the first dielectric
layer.
32. A method of forming a semiconductor structure, comprising:
forming a first dielectric layer over a substrate; forming a via
opening in the first dielectric layer; forming a conductive layer
in the via opening and over the first dielectric layer; forming an
opening in the conductive layer to expose a portion of the first
dielectric layer; and forming a second dielectric layer over the
conductive layer by a spin-on coating process, such that the second
dielectric layer over the opening of the conductive layer is
separated from the exposed portion of the first dielectric layer by
an air gap having a top in a position higher than a top of the
conductive layer.
33. The method of claim 32, wherein the forming the first
dielectric layer comprises forming in sequence a low-k dielectric
layer and an etch stop layer over the substrate, wherein the method
further comprises performing an etching process to the exposed
portion of the first dielectric layer prior to the forming the
second dielectric layer, such that the etch stop layer in the
exposed portion is removed.
34. The method of claim 33, further comprising forming a barrier
layer in the via opening and over the first dielectric layer prior
to the forming the conductive layer, wherein the conductive layer
is formed over the barrier layer, and the forming the opening in
the conductive layer further forms an opening in the barrier layer
to expose the portion of the first dielectric layer.
35. The method of claim 32, further comprising forming a capping
layer over the conductive layer prior to the forming the second
dielectric layer, wherein the second dielectric layer is formed
over the capping layer.
36. The method of claim 32, further comprising performing a
chemical mechanical polishing (CMP) process to the conductive layer
prior to the forming the opening in the conductive layer, wherein
the CMP process stops before reaching the first dielectric
layer.
37. The method of claim 1, wherein the removing the first portion
of the substrate is such that the sidewall of the remaining second
portion of the substrate is curved.
Description
BACKGROUND
[0001] The semiconductor integrated circuit (IC) industry has
experienced rapid growth. Technological progress in IC manufacture
has produced several generations of ICs, and each generation
fabricates smaller and more complex circuits than the previous
generation. Currently, the semiconductor industry has progressed
into nanometer technology nodes for higher device density and
better electrical performance. In the past, the reductions of the
feature size were limited by the ability to define the structures
photo-lithographically. Recently, device geometries having smaller
dimensions created new challenges. For example, for two adjacent
conductive lines, when the distance between the conductive lines is
decreased, the semiconductor devices suffer from several electrical
and processes issues. Conventional techniques have not been
entirely satisfactory in all respects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Aspects of the present disclosure are best understood from
the following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
[0003] FIG. 1A is a flow chart illustrating a method of forming a
semiconductor structure according to some embodiments of the
present disclosure.
[0004] FIG. 1B is a flow chart illustrating a method according to
various embodiments of the present disclosure.
[0005] FIGS. 2-13 are drawings schematically illustrating a method
of forming a semiconductor structure in various process stages
according to various embodiment of the present disclosure.
DETAILED DESCRIPTION
[0006] The following disclosure provides many different
embodiments, or examples, for implementing different features of
the provided subject matter. Specific examples of components and
arrangements are described below to simplify the present
disclosure. These are, of course, merely examples and are not
intended to be limiting. For example, the formation of a first
feature over or on a second feature in the description that follows
may include embodiments in which the first and second features are
formed in direct contact, and may also include embodiments in which
additional features may be formed between the first and second
features, such that the first and second features may not be in
direct contact. In addition, the present disclosure may repeat
reference numerals and/or letters in the various examples. This
repetition is for the purpose of simplicity and clarity and does
not in itself dictate a relationship between the various
embodiments and/or configurations discussed.
[0007] The semiconductor industry has continually improved the
speed and power of integrated circuits (ICs) by reducing the size
of components within the ICs. Several advanced techniques have been
developed to implement technique nodes with smaller feature sizes.
When the spacing between two adjacent conductive lines is smaller
than a certain dimension, the semiconductor suffers from several
issues such as RC delay, time dependent dielectric breakdown
(TDDB), and parasitic capacitance. To improve these issues, an air
gap is formed between two adjacent conductive lines as air has a
low dielectric constant of 1. However, when the spacing between two
adjacent conductive line is smaller than a certain dimension such
as for example about 50 nm or less, conventional processes in the
back-end of line (BEOL) suffer from process problems that degrade
device performance and decrease the manufacture yield. Accordingly,
one of the aspects of the present disclosure is to provide a
solution to these problems.
[0008] The present disclosure relates generally to a semiconductor
structure and a method of manufacturing the semiconductor
structure. In embodiments, the method disclosed herein may be
applied in BEOL, for example. According to various embodiments of
the present disclosure, the method disclosed herein may form an
in-situ air gap, which is self-aligned, between two adjacent
conductive lines. Various embodiments of the present disclosure
will be described in detail hereinafter.
[0009] It will be understood that, although the terms first,
second, etc. may be used herein to describe various elements, these
elements should not be limited by these terms. These terms are only
used to distinguish one element from another. For example, a first
element could be termed a second element, and, similarly, a second
element could be termed a first element, without departing from the
scope of the embodiments. As used herein, the term "and/or"
includes any and all combinations of one or more of the associated
listed items.
[0010] Further, spatially relative terms, such as "beneath,"
"below," "lower," "above," "upper" and the like, may be used herein
for ease of description to describe one element or feature's
relationship to another element(s) or feature(s) as illustrated in
the figures. The spatially relative terms are intended to encompass
different orientations of the device in use or operation in
addition to the orientation depicted in the figures. The apparatus
may be otherwise oriented (rotated 90 degrees or at other
orientations) and the spatially relative descriptors used herein
may likewise be interpreted accordingly.
[0011] It will be understood that when an element is referred to as
being "connected" or "coupled" to another element, it can be
directly connected or coupled to the other element or intervening
elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directly coupled" to another
element, there are no intervening elements present.
[0012] FIG. 1A is a flow chart illustrating a method 10 of forming
a semiconductor structure according to some embodiments of the
present disclosure. The method 10 includes operation 11, operation
12, operation 13, operation 14, operation 15, and operation 16.
FIGS. 2-13 collectively illustrate more detailed manufacturing
methods as a series of cross-sectional views or plan views in
accordance with some embodiments of the present disclosure. It will
be appreciated that although these methods each illustrate a number
of operations, acts and/or features, not all of these operations,
acts and/or features are necessarily required, and other
un-illustrated operations, acts and/or features may also be
present. Also, the ordering of the operations and/or acts in some
embodiments can vary from what is illustrated in these figures. In
addition, the illustrated acts can be further divided into sub-acts
in some implementations, while in other implementations some of the
illustrated acts can be carried out concurrently with one
another.
[0013] Referring to FIG. 1A, the method 10 includes an operation 11
of forming a first dielectric layer over a substrate. FIG. 2 is a
cross-sectional view schematically illustrating the formation of a
first dielectric layer 110 over a substrate 101 according to some
embodiments of the present disclosure.
[0014] In some embodiments, the substrate 101 may include a bulk
silicon substrate. In yet some embodiments, the substrate 101
include an elementary semiconductor such as for example germanium
or silicon in a crystalline structure. In yet some embodiments, the
substrate 101 include a compound semiconductor such as for example
gallium arsenic, silicon carbide, indium phosphide, gallium
phosphide or indium antimonide, or combinations thereof. In yet
some embodiments, the substrate may include an alloy semiconductor
such as silicon germanium, silicon germanium carbide, gallium
arsenic phosphide, and gallium indium phosphide. In some
embodiments, the substrate 101 may include an integrated circuit
103. The integrated circuit 103 may include active devices such as
transistors and the like. The substrate 101 may include dielectric
layer and via contacts (not shown in FIG. 2) over the integrated
circuit 103. The via contacts may be fabricated over the integrated
circuit 103 such that the integrated circuit 103 may be
electrically connected with other devices. In some embodiments, the
substrate 101 has experienced processes of the front-end of line
and a middle-end of line.
[0015] In some embodiments, the first dielectric layer 110 may
include oxides such as silicon oxide, undoped silicate glass (USG),
borophosphosilicate glass (BPSG), fluorinated silicate glass (FSG).
In some embodiments, the first dielectric layer 110 may include
low-k dielectrics such as carbon doped oxides, porous carbon doped
silicon dioxide, a polymer such as polyimide, the like, or a
combination thereof. The low-k dielectric materials may have k
values lower than 3.9. The first dielectric layer 110 may be
deposited by physical vapor deposition (PVD) processes, chemical
vapor deposition (CVD) processes, atomic layer deposition (ALD)
processes, a spin-on-dielectric (SOD) process, and the like.
[0016] In yet some embodiments, the first dielectric layer 110
includes a low-k layer 114 over the substrate 101 and an etching
stop layer 116 on the low-k layer 114. Illustrative examples of the
material of the etching stop layer 116 include TiN, SiN,
Al.sub.xO.sub.yN.sub.z, nitrogen doped silicon carbide, the like,
and a combination thereof. The etching stop layer 116 may be formed
by techniques such as for example PVD, CVD, SOD, ALD, and the
like.
[0017] Referring to FIG. 1A, the method 10 proceeds to operation 12
by forming a via opening in the first dielectric layer. FIGS. 3-4
are cross-sectional view schematically illustrating the detailed
steps of forming a via opening 112 in the first dielectric layer
110 according to some embodiments of the present disclosure. In
FIG. 3, a patterned masking layer 117 with one or more opening 117a
are formed over the first dielectric layer 110. The patterned
masking layer 117 may include a photoreist layer or a hard mask
layer. The illustrated patterned masking layer 117 may include a
bottom layer, a middle layer, an antireflective coating (not
shown), and/or the like. In FIG. 4, an etching process is performed
to form one or more via openings 112 in the first dielectric layer
110. The etching process may includes wet etching processes or dry
etching process such as for example reactive ion etching techniques
or plasma etching techniques. After forming the via opening 112,
the patterned masking layer may be removed according to some
embodiments of the present disclosure.
[0018] Referring to FIG. 1A and FIG. 5, the method 10 proceeds to
operation 13 by forming a barrier layer 120 lining the via opening
112 and covering the first dielectric layer 110. Illustrative
examples of the material of the barrier layer 120 includes Ta, TaN,
and Co, the like, and a combination thereof. The barrier layer 120
may prevent the metallic material, which is formed in subsequent
processes, from migration to the first dielectric layer 110
according to some embodiments of the present disclosure.
[0019] Referring still to FIG. 1A, the method 10 proceeds to
operation 14 by forming a conductive layer overlaying the barrier
layer and filling the via opening. FIGS. 6-7 are cross-sectional
view schematically illustrating the detailed steps of operation 14.
In FIG. 6. a metal layer 130'' is deposed overlaying the barrier
layer 120 and filling the via opening 112. In FIG. 7, a
planarization process such as for example chemical mechanical
polishing (CMP) process may be carried out on the top of the metal
layer 130'' so as to form the conductive layer 130. The conductive
layer 130 is formed overlaying the barrier layer 120 and filling
the via opening 112. Illustrative examples of conductive layer 130
includes Cu, Al, W, Co, the like, and a combination thereof. The
conductive layer 130 includes a first portion 130a filled in the
via opening 112. The first portion 130a and the barrier layer 120
in the via opening 112 collectively constitutes one or more via
contacts 134 for vertical interconnection. The conductive layer 130
further includes a second portion 130b over the first dielectric
layer 110 and the barrier layer 120. The planarization process does
not remove all of the second portion 130b of the metal layer 130'',
and most of the second portion 130b of the metal layer 130'' may be
left. Accordingly, the planarization process disclosed herein
differs essentially from the CMP used in the damascene or dual
damascene processes.
[0020] Turning back to FIG. 1A, the method 10 proceeds to operation
15 by patterning the conductive layer and the barrier layer to form
a first conductive portion, a second conductive portion, and a
spacing there between. FIGS. 8 and 9A are cross-sectional view
schematically illustrating the detailed steps of operation 15
according to some embodiments of the present disclosure. As shown
in FIG. 8, a masking layer 150 is formed over the conductive layer
130. The masking layer 150 has a pattern with one or more openings
151 exposing portions of the conductive layer 130. In some
embodiments, the masking layer 150 may be a single-layered
structure or a multiple-layered structure including a bottom layer,
a middle layer, an antireflective coating, and/or the like. Next,
as shown in FIG. 9A, the conductive layer 130 and the barrier layer
120 are patterned to form a first conductive portion 131, a second
conductive portion 132, and a spacing 135 between the first
conductive portion 131 and second conductive portion 132. In some
embodiments, pattering the conductive layer 130 and the barrier
layer 120 includes transferring the pattern of the masking layer
150 to the conductive layer 130 and the barrier layer 120. For
example, patterning the conductive layer 130 and the barrier layer
120 may include selectively etching the conductive layer 130 and
the barrier layer 120, thereby forming the first conductive portion
131, the second conductive portion 132, and the spacing 135. In
some embodiments, at least one of the first and second conductive
portions 131, 132 is physically connected to the via contacts 134.
The spacing 135 may cut through both of the conductive layer 130
and the barrier layer 120. Accordingly, the remained portions 120r
of the barrier layer 120 are under the first conductive portion 131
and the second conductive portion 132. In addition, the spacing 135
reveals or exposes a portion of the first dielectric layer 110. For
example, the exposed portion of the first dielectric layer 110 may
be a portion 116a of the etching stop layer 116 of the first
dielectric layer 110, as shown in FIG. 9A. In some embodiments, the
selectively etching process may includes wet etching processes or
dry etching process such as for example plasma etching techniques
or reactive ion etching (RIE) techniques. In examples, the
selectively etching process employs RIE techniques using etchant
including at least one of Cl.sub.2, F.sub.2, H.sub.2, and
C.sub.xF.sub.y such as CF.sub.4, CHF.sub.3, CH.sub.2F.sub.2,
C.sub.2HF.sub.5, and C.sub.2H.sub.2F.sub.4.
[0021] Referring to FIG. 9B, the masking layer 150 may be removed
after the formation of the first conductive portion 131, the second
conductive portion 132, and the spacing 135, according to some
embodiments of the present disclosure.
[0022] It various embodiments, the first and second conductive
portions 131, 132 are not completely formed or embedded in the
trenches or vias of the first dielectric layer 110, and therefore
the first and second conductive portions 131, 132 are different
from the damascene conductive regions. In some embodiments, the top
surfaces 131t of the first conductive portions 131 and the top
surface 132t of the second conductive portions 132 extend at a
substantially identical level that is higher than a top surface
110t of the first dielectric layer 110. Further, the sidewalls
131s, 132s of the first and second conductive portions 131, 132 are
exposed and constitutes the lateral surfaces of the spacing 135.
Accordingly, the embodiments disclosed herein differs essentially
from the damascene or dual damascene processes.
[0023] As shown in FIG. 9B, the spacing 135 may include an inlet
135i having a width W1 and a bottom 135b having a width W2. The
width W1 of the inlet 135i is greater than the width W2 of the
bottom 135b according to some embodiments of the present
disclosure. In some examples, the width W1 of the inlet 135i may be
ranged from about 60 nm to about 5 nm, more specifically from about
50 nm to about 5 nm. For example, the width W1 may be about 5 nm, 7
nm, 10 nm, 20 nm, and 40 nm. In addition, the width W2 of the
bottom 135b may be ranged from about 50 nm to about 3 nm,
specifically from about 45 nm to about 5 nm, more specifically from
about 40 nm to about 16 nm.
[0024] FIG. 9C illustrates a top view of FIG. 9B according to some
embodiments of the present disclosure, in which FIG. 9B is taken
along line A-A' in FIG. 9C. As shown in FIG. 9C, the first
conductive portion 131 and second conductive portion 132 are
conductive lines or wirings so that the first conductive portion
131 and second conductive portion 132 may also refer to a first
conductive wiring 131 and second conductive wiring 132 in some
embodiments of the present disclosure. Further, the spacing 135 is
present between the first conductive portion 131 and second
conductive portion 132. In some embodiments, the first conductive
portion 131, the second conductive portion 132, and the spacing 135
extend along a first direction D1. In examples, the first
conductive portion 131, the second conductive portion 132, and the
spacing 135 may be substantially parallel with each other.
[0025] Referring to FIG. 10, the method 10 may optionally include
an act of selectively etching the first dielectric layer 110 to
form an aperture 137 under the spacing 135, after forming the first
conductive portion 131, the second conductive portion 132, and the
spacing 135. In some embodiments, selectively etching the first
dielectric layer 110 includes removing the exposed portion 116a of
the etching stop layer 116 of the first dielectric layer 110 using
the first and second conductive portions 131, 132 as a mask,
thereby forming an aperture 137 under the spacing 135. In some
examples, the aperture 137 has a width W3 less than the width W1 of
the inlet 135i of the spacing 135(shown in FIG. 9B). In yet some
examples, the width W3 of the aperture 137 is greater than the
width W2 of the bottom 135b of the spacing 135 (shown in FIG. 9B).
In yet some embodiments, the aperture 137 communicates with the
spacing 135. The spacing 135 and the aperture 137 collectively form
a void region 136. The spacing 135 forms an upper portion of the
void region 136, and may also refer to as the upper portion 135 of
the void region 136. The aperture 137 forms a bottom portion of the
void region 136, and may also refer to as the bottom portion 137 of
the void region 136. In some examples, the void region 136 includes
a neck portion 136n, which has a minimum width W4 through out the
void region 136. The ratio of the width W4 of the neck portion 136n
to the width W5 of the inlet 136i of the void region 136 may be
ranged from about 0.5 to about 0.95, specifically from 0.6 to 0.95,
more specifically from 0.8 to 0.95. It is noted that the width W5
of the inlet 136i may be the same as or different from the width W1
of the inlet 135i of the spacing 135. In some embodiments, the
width W1 of the inlet 135i is possibly changed during selectively
etching the etching the stop layer 116 of the first dielectric
layer 110. In embodiments, the selectively etching process may
includes wet etching processes or dry etching process such as for
example plasma etching techniques and/or reactive ion etching (RIE)
techniques.
[0026] Referring to FIG. 11, after the formation of the aperture
137, the method 10 may optionally include an act of forming a
capping layer 138 covering the first and second conductive portions
131, 132. In some embodiments, the capping layer 138 covers the top
and sidewalls of each of the first and second conductive portions
131, 132. Accordingly, the first and second conductive portions
131, 132 are encapsulated by the capping layer 138 and the remained
portions 120r of the barrier layer 120. In some examples, the
capping layer 138 includes material such as for example cobalt
silicide (Co--Si.sub.x), Co, Mn, Ru, the like, and a combination
thereof. The capping layer 138 and the remained portions 120r of
the barrier layer 120 may suppress or prevent the material of the
conductive portions 131, 132 from migration to the dielectric
formed in the subsequent processes.
[0027] In yet some embodiments, the capping layer 138 may be formed
prior to the formation of the aperture 137. For example, the
capping layer 138 may be formed immediately after the patterning of
the conductive layer 130 and the barrier layer 120 depicted in FIG.
9B.
[0028] Referring back to FIG. 1A, the method 10 proceeds to
operation 16 by forming a second dielectric layer covering the
spacing and the first and second conductive portions to enclose a
void gap in the spacing. FIG. 12 A is a cross-sectional view
illustrating the formation of a second dielectric layer 140. The
second dielectric layer 140 covers the first and second conductive
portions 131, 132 and the void region 136 (or spacing 135) there
between. It is noted that the void region 136 is not filled with
the second dielectric layer 140 so that an in-situ formed void gap
142 is fabricated at the position of the void region 136 between
the first and second conductive portions 131, 132. The void gap 142
may also referred to as an air gap 142. In some embodiments, the
second dielectric layer 140 may be formed by non-conformal chemical
vapor deposition techniques, spin-on coating techniques, and the
like. The void gap 142 may be formed under the second dielectric
layer 140 by selecting suitable material for the deposited material
and/or process parameters. Illustrative examples of suitable
materials for the second dielectric layer 140 includes, but not
limited to, nitrogen doped silicon carbide, oxygen doped silicon
carbide, TEOS, Si.sub.3N.sub.4, and the low-k material, and the
like. The air gap or void gap 142 with low dielectric constant
(e.g., 1) may improve various electrical interferences between the
first and second conductive portions 131, 132, such as the
parasitic capacitance and RC delay of the conductive features of
back-end of line (BEOL). Further, electromigration (EM) and time
dependent dielectric breakdown (TDDB) of devices may be
improved.
[0029] FIG. 12 B is a top view illustrating the structure of FIG.
12A, in which FIG. 12 A is taken along line A-A' in FIG. 12B. The
void gap 142 is in-situ formed in position of the void region 136
(or spacing) between the first and second conductive portions 131,
132. Furthermore, the void region 136 (or spacing) may be
concurrently formed with the first and second conductive portions
131, 132 according to some embodiments of the present disclosure.
Therefore, the formation of the air gap or void gap 142 does not
require an addition photolithographic process so that the method
disclosed herein is cost effective, according to some embodiments
of the present disclosure. Furthermore, in convention methods where
the air gap is formed using an addition mask, it suffers
misalignment issues in advanced technical nodes. To the contrary,
the embodiments disclosed herein advantageously involves an in-situ
method of forming the air gap or void gap between the first and
second conductive portions 131, 132, and therefore the misalignment
issues in convention techniques are avoid.
[0030] After operation 16, the method 10 may include other
operations or steps. FIG. 13 illustrates additional via contacts
144 formed in second dielectric layer 140, and conductive lines
161, 162 formed over the second dielectric layer 140. The via
contacts 144 are electrically coupled to the respective underlying
conductive portions 131, 132. The conductive lines 161, 162 are
disposed over and electrically coupled to respective underlying via
contacts 144. A dielectric layer 170 is formed covering the
conductive lines 161, 162 and the second dielectric layer 140. An
air gap 164 may be formed the between conductive lines 161 and 162
and between the dielectric layers 170 and 170. The formation
process may be essentially the same as in FIGS. 2 through 12A, and
are not repeated herein.
[0031] FIG. 1B is flowchart illustrating a method 20 according to
various embodiments of the present disclosure. The method 20
includes an operation 21 of forming a conductive layer over a
precursor substrate. FIG. 7 illustrates the formation of a
conductive layer 130 over a precursor substrate 200. In some
embodiments, the precursor substrate 200 may include a substrate
101, a first dielectric layer 110 over the substrate 101, a via
opening 112 formed in the first dielectric layer 110. In yet some
embodiments, the precursor substrate 200 further includes a barrier
layer 120 on the first dielectric layer 110 and lining the via
opening 112. In yet some embodiments, the conductive layer 130 may
fill the via opening 112 and cover the first dielectric layer 110.
The portion of the first dielectric layer 110 filled in the via
opening 112 constitutes a via contact 134 in the first dielectric
layer 110 according to some embodiments of the present
disclosure.
[0032] Referring to FIG. 1B, the method 20 proceeds to operation 22
by selectively etching the conductive layer to form a first
conductive portion, a second conductive portion, and a spacing
between the first conductive portion and the second conductive
portion. Referring to FIG. 9B, the conductive layer 130 is
selectively etched to form a first conductive portion 131, a second
conductive portion 132, and a spacing 135. The spacing 135 between
the first conductive portion 131 and the second conductive portion
132. In some embodiments, the spacing 135 includes an inlet 135i
and a bottom 135b, and the width of the inlet is greater than a
width of the bottom.
[0033] After operation 22, the method 20 may optionally includes an
act of removing a portion 116a of the precursor substrate between
the first conductive portion 131 and the second conductive portion
132 according to some embodiments of the present disclosure. The
resulting structure is shown in FIG. 10. The removal of the portion
116a forms an aperture 137 under the spacing 135. The spacing 135
and the aperture 137 collectively constitutes a void region
136.
[0034] Referring to FIG. 11, the method 20 may optionally includes
an act of forming a metal capping layer 138 covering the first and
second conductive portions 131, 132 after the formation of the
aperture 137. However, in yet some embodiments, the metal capping
layer 138 may be formed prior to the formation of the aperture 137.
For example, the capping layer 138 may be formed immediately after
the formation of the first conductive portion 131 and the second
conductive portion 132 depicted in FIG. 9B.
[0035] Referring to FIG. 1B, the method 20 proceeds to operation 23
by forming a dielectric layer over the first conductive portion,
the second conductive portion, and the spacing, such that an air
gap is formed in the spacing between the first and second
conductive portions and is sealed by the dielectric layer. FIG. 12A
illustrates the formation of a dielectric layer 140. The dielectric
layer 140 is over the first conductive portion 131, the second
conductive portion 132, and the spacing 135. An air gap 142 is
formed in the spacing or the void region 136 under the dielectric
layer 140 between the first and second conductive portions 131,
132. The spacing or the void region 136 is not filled with the
dielectric layer 140 so to form the air gap 142 under the
dielectric layer 140. The air gap 142 is sealed by the dielectric
layer 140.
[0036] According to another aspect of the present disclosure, a
semiconductor structure is provided. FIG. 12A illustrates a
cross-sectional view of a semiconductor structure 300 according to
various embodiments of the present disclosure. FIG. 12B is a top
view of FIG. 12A according to some embodiments of the present
disclosure. FIG. 12A is approximately taken along line A-A' in FIG.
12B. As shown in FIGS. 12A and 12B, the semiconductor structure 300
includes a first dielectric layer 110, a first conductive wiring
131, a second conductive wiring 132, a second dielectric layer 140
and an air gap 142 (also referred to as void gap 142).
[0037] The first conductive wiring 131 and second conductive wiring
132 extend over the first dielectric layer 110. The first
conductive wiring 131 and the second conductive wiring 132
respectively have a first sidewall 131s and a second sidewall 132s.
The second sidewall 132s is opposite to the first sidewall 131s.
The first sidewall 131s and the second sidewall 132s form an acute
angle .theta.. In some embodiments, the acute angle .theta. may be
ranged from about 5 degrees to about 40 degrees, for example about
7 degrees, about 12 degrees, about 15 degrees, about 20 degrees,
and about 30 degrees. A spacing is presented between the first
sidewall 131s and the second sidewall 132s.
[0038] The second dielectric layer 140 is disposed over the first
conductive wiring 131 and the second conductive wiring 132. The
second dielectric layer 140 seals the spacing between the first and
second sidewalls 131s, 132s. The second dielectric layer 140 does
not fully fill the spacing between the first and second sidewalls
131s, 132s. An air gap 142, therefore, is formed under the second
dielectric layer 140 and between the first and second sidewalls
131s, 132s.
[0039] In some embodiments, as shown in FIG. 12B, the second
conductive wiring 132 may extend in an extension direction D1. The
second conductive wiring 132 is at least partially aligned with the
first conductive wiring 131 in a perpendicular direction D2, which
is orthogonal to the extension direction D1. In some examples, the
second conductive wiring 132 has a section 132a aligned with the
first conductive wiring 131. The length L1 of the air gap 142 along
the extension direction D1 is substantially equal to the length L2
of the section 132a of the second conductive wiring 132. The term
"substantially equal to" herein refers to that the difference
between the length L1 and the length L2 is less than or equal to
triple width W1 of the air gap 142, in which the width W1 is the
maximum width of the air gap 142. In some examples, the length L1
and the length L2 satisfy the following formula (I):
|L1-L2|<(3.times.W1) formula (I).
[0040] In yet some examples, the length L1 and the length L2
satisfy the following formula (II):
|L1-L2|<(2.times.W1) formula (II).
[0041] In yet some examples, the length L1 and the length L2
satisfy the following formula (III):
|L1-L2|<(W1) formula (III).
[0042] In yet some embodiments, a third conductive wiring 133 is
included in the semiconductor structure 300, as shown in FIG. 12B.
The first conductive wiring 131 extends in a direction D1, and has
a section 131a aligned with the third conductive wiring 133 in a
perpendicular direction D2. An air gap 143 is existed between the
conductive wiring 131 and the third conductive wiring 133. The
length L3 of the air gap 143 along the direction D1 is
substantially equal to the length L3 of the section 131a of the
first conductive wiring 131. In some examples, the air gap 143 and
the air gap 142 are arranged at opposite sides of the first
conductive wiring 131. Furthermore, the length L3 of the air gap
143 is different from the length L1 a of the air gap 142.
[0043] In yet some embodiments, the air gap 142 includes an upper
portion 135(indicated in FIG. 10), a bottom portion 137, and a neck
portion 136n there between, the neck portion 136n has a minimum
width W4 from the upper portion 135 to the bottom portion 137. In
some examples, the upper portion 135 has a maximum width W5, and a
ratio of the minimum width W4 to the minimum width W5 is ranged
from about 0.5 to about 0.95. In some examples, the bottom portion
137 of the air gap 142 extends into the first dielectric 110.
[0044] In yet some embodiments, one or more via contacts 134 may be
included in the semiconductor structure 300. The via contacts 134
is formed or embedded in the first dielectric layer 110. The via
contact 134 is connected to at least one of the first and second
conductive wirings 131, 132.
[0045] In accordance with one aspect of some embodiments, a method
includes the following operations: forming a conductive layer over
a precursor substrate; selectively etching the conductive layer to
form a first conductive portion, a second conductive portion, and a
spacing between the first conductive portion and the second
conductive portion; and forming a dielectric layer over the first
conductive portion, the second conductive portion, and the spacing,
such that an air gap is formed in the spacing between the first and
second conductive portions and is sealed by the dielectric
layer.
[0046] In accordance with another aspect of some embodiments, a
method of forming a semiconductor structure includes the following
operations: forming a first dielectric layer over a substrate;
forming a via opening in the first dielectric layer; forming a
barrier layer lining the via opening and covering the first
dielectric layer; forming a conductive layer overlaying the barrier
layer and filling the via opening; patterning the conductive layer
and the barrier layer to form a first conductive portion, a second
conductive portion, and a spacing there between; and forming a
second dielectric layer covering the spacing and the first and
second conductive portions to enclose a void gap in the
spacing.
[0047] In accordance with another aspect of some embodiments, a
semiconductor structure includes a first dielectric, a first
conductive wiring, a second conductive wiring, and a second
dielectric layer. The first conductive wiring extends over the
first dielectric layer and has a first sidewall. The second
conductive wiring extends over the first dielectric layer and has a
second sidewall opposite to the first sidewall. The second
dielectric layer is over the first conductive wiring and the second
conductive wiring. The air gap is under the second dielectric layer
between the first sidewall and the second sidewall. The first
sidewall and the second sidewall form an acute angle.
* * * * *